Minimally invasive surgical techniques are known for performing medical procedures within all parts of the cardiovascular system. Exemplary known procedures include the steps of passing a small diameter, highly-flexible catheter through one or more blood vessels and into the heart. When positioned as desired, additional features of the catheter are used, in conjunction with associated equipment, to perform all or a portion of a medical treatment, such as vessel occlusion, tissue biopsy, or tissue ablation, among others. Almost always, these procedures are performed while the heart is beating and blood is flowing. Not surprisingly, even though visualization and positioning aids are adequate for general placement of the device, maintaining the device in a selected position and orientation can be difficult as the tissue moves and blood flows, especially during a procedure that must be done quickly. As diagnostic and visualization equipment and techniques have continued to evolve, it has become possible to identify tissue areas to be treated with greater precision than the ability to quickly situate the device and effectuate treatment.
In addition to the challenges presented by moving tissue and flowing blood, the actual topography of the tissue being treated presents challenges. For example, unlike stylized drawings that depict the interior of the chambers of the heart as having smooth, evenly curved walls leading neatly to tubular blood vessels, the interior surfaces of the heart's chambers are irregular, uneven, and fibrous, as are the openings to blood vessels. Thus, for procedures that call for uniform tissue contact or tissue contact along an extended line, the structure and techniques for use of known devices can be deficient in some regards. For example, difficulties may arise in properly placing and holding a device in position at the desired orientation due to the uneven topography of the targeted tissue. Further, even if the device is suitable for the tissue topography at the treatment site, variations in physiological anatomy may occur from one patient to the next, further complicating the use of a particularly-dimensioned device. Additional difficulty may stem from applying excessive force to the device to maintain contact between the device and the tissue, instead resulting in tissue damage or the inadvertent displacement of the device downstream in a particular vessel or organ.
By way of example, catheter-based devices are known for placement in the left atrium for ablating tissue within the atrium for the purpose of electrically isolating one or more pulmonary veins from the atrium in an attempt to increase the success rate of atrial fibrillation ablation. Given the uneven topography of the tissue, anatomical differences between patients, and the tortuous environment of the blood flowing through the vasculature mentioned above, secure placement of a device against a pulmonary vein can be challenging. Moreover, if too much force is applied to the device and thus the tissue, risk of damaging the pulmonary vein increases—e.g., the vein could be deformed, ruptured, stenosed, or otherwise injured. In view of the above, it would be desirable to provide a medical device and treatment methods of use thereof that allow for secure placement against uneven, topographical surfaces such as those found in the left atrium of the heart while reducing or otherwise minimizing the risk of unwanted injury to the tissue region being treated.